A/C only blows hot

[MDYLANP]

So yesterday my A/C was ice cold thanks basically replacing everything last summer. But today after running the heater on defroster for about 5 minutes this morning, it only blows hot air. When I switch to heat, it gets warmer but it's still freaking hot when the hvac is all the way cold. And it's like recently the vent selector isn't working right. It blows like 50/50 head and feet when in the head position. Full feet works fine. I know that's just a blend door problem but I'm. It sure about the hot A/C. Any thoughts?

 

[east302]

Based on the dial positions, the HVAC control panel send voltage signals to adjust two damper actuators under the dash. One actuator adjusts the damper for defrost/vent/floor and the other directs air either over the heater coil for full heat or diverts it for full cold.

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I guess, then, that you've either got a control panel not sending the voltage to the actuator or you have a stuck/bad actuator or the damper itself came off of the actuator. The same goes for the mode actuator as well. I suppose you could check for voltage at the temperature actuator connector, but maybe some others can offer other means for testing it. I believe there is a small dial on the actuator that turns as the actuator adjusts, so that may be one way to see if it is actually responding to the control panel dial selection.

 

[MDYLANP]

Thanks man, I didn't realize the temp settings were affected by a blend door as well. I'm sure that one of those is my problem then. I changed my entire AC system last summer. So if the door isn't receiving signal, it'd be due to faulty wiring somewhere between the hvac and the actuator. Hopefully it's either stuck or just off the arm. Do you have a link on replacing the actuator in case they end up being bad.

 

[east302]

It's just screwed into place so it's easy to remove. The hard part is getting to it. Here is the install method from alldata for a 1998 K1500, you can probably disregard the part about rolling the dash as I've seen where others managed to remove the part without going to that extreme.

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Remove or Disconnect

1. Negative battery cable.
2. Roll instrument panel forward.
3. Electrical connector.
4. Screws.
5. Actuator.

Adjust

1. Electrical connector to the actuator.
2. Turn the ignition key to the run position and let the actuator position itself.
3. Turn off the ignition key.
4. Remove the actuator from the electrical connector.

Install or Connect

1. Actuator.
2. Screws.
3. Electrical connectors.
4. Instrument panel compartment.
5. Negative battery cable.
6. Check circuit operation.

I don't see a wiring diagram for the particular part, but here is a description of the operation so it may help checking for voltage. There's got to be a way to check that you're actually getting voltage to the actuator from the control panel before going through the trouble of removing the actuator. Again, this is for a 1998 and I understand that 1995 had a different wiring harness or something so it may be different for yours:

The Front Mode Door Motor, the Front Temperature Door Motor, and the Recirculation Door Motor are powered by the BRN (141) wires when the Ignition Switch is in RUN. Grounding for the door motors is through the BLK (150) wires to Ground G202.The HVAC Control Module is powered when the Ignition Switch is in RUN by the BRN (141) wires. Grounding is through the BLK (150) wire to Ground G200 for the IP.

The HVAC Control Module's ventilation controls for the Front Mode Door and the Recirculation Door are disabled when the Module's Front Blower Switch is in the OFF position. With the Front Blower Switch in the HI, M2, M1, or LO positions, the ventilation controls are enabled. The Front Temperature Door is not dependent on Front Blower Motor operations and can be controlled as long as the Ignition Switch is in RUN.

The Mode and Temperature Doors are positioned in proportion to the variable voltage signal received from the HVAC Control Module. Adjusting the Temperature Dial at the HVAC Control Module adjusts a rheostat which provides a voltage signal proportional to the dial position. This voltage is carried on the LT BLU (733) wire to the Front Temperature Door Motor which then positions in response to the voltage signal. Adjusting the Mode Dial at the HVAC Control Module adjusts a rheostat which provides a voltage signal proportional to the dial position. This voltage is carried on the WHT (454) wire to the Front Mode Door Motor which then positions in response to the voltage signal.

The Recirculation Door is a two-position door and is in the Recirculation position only when the input DK GRN (1614) wire is grounded through the HVAC Control Module. For air conditioned vehicles with 7.4 Liter Gasoline Engines, the Recirculation Door is also grounded when the Auxiliary Cooling Fan A/C Pressure Switch operates the Auxiliary Cooling Fan. The door is normally in the Outside Air position but moves to the Inside Air position when the input wire is grounded. A LED on the HVAC Control Module is illuminated when the Recirculation Door is grounded through the HVAC Control Module.

 

[MDYLANP]

Wow that's awesome. Thanks so much. Guess I know what I'm going to be trying this weekend.

 

[Blue95]

Did replacing the mode actuator fix this? or the HVAC controller?

I am having an issue where the A/C is ice cold when on defrost, but when on feet or vent it is warm and you can see the actuator go back to mixed blend or if the A/C is off and temp still cold it goes back to mixed blend, then it goes to only cold air when the defrost is turned on....